An error has been seen with SOME Gertduinos where the Raspberry-Pi does not boot or no remote shell acecss is possible.
The cause of the error is the ATmega48 device which pulls the scl line low. This is equivalent to the 'safe boot' mode
of the Raspberry-Pi. The suspicion is that for some boards the factory did not clear the test program from the Atmega48.
This by itself does not cause problems except when used with NOOBS 1.2. In that case the boot process stops
with the 'colour' screen visible. The error is NOT seem with NOOBS 1.3 or with Rasbian.
In all cases holding the Atmega48 in reset by placing a jumper over the Re pins solves the issue.
After clearing the Atmega48 or programming it with any program which does not hold the SCL pin
low the error goes away and the jumper is no longer needed.
Clearing device can be done with avrdude. You need first set the programming jumpers for the Atmega48
device as shown in the manual. As specified in the manual you need a version of avrdude which has been
updated to work with the Raspberry-Pi GPIO pins.
After installing that you can erase the Atmega48 device using:
/usr/bin/avrdude -c gpio -p m48pa -e